Materials Characterization Paper
In Support of the
Identification of Nonhazardous Secondary Materials That Are Solid Waste
Auto Shredder Residue
March 18, 2010
1. Definition of Auto Shredder Residue
Auto shredder residue (ASR) is the 15 to 20 percent of vehicle materials remaining after a
vehicle has been shredded and removed of reusable parts and metals. ASR is composed of
plastics, rubber, foam, residual metal pieces, paper, fabric, glass, sand, and dirt (EPA, 2008;
USCAR, 2008). It is also termed “auto fluff” or “auto shredder fluff.”
2. Annual Quantities of Auto Shredder Residue Generated and Used
(1) Sectors that generate auto shredder residue
Auto shredding operations, categorized under NAICS 423930 (Recyclable
Material Merchant Wholesalers) are the only known generators of ASR. There
are approximately 185 to 200 auto shredders in the U.S. (Boughton, 2006;
(2) Quantities of auto shredder residue generated
The U.S. generates approximately 5 million tons of ASR annually and nearly all
of this is landfilled (Hook, 2008; EPA, 2008).
(3) Trends in generation of auto shredder residue
Quantities of ASR produced are likely to increase in the future, due to the
growing number of cars scrapped each year and the increased use of plastics in
automobile production (Nourreddine, 2007).
3. Uses of Auto Shredder Residue
(1) Combustion uses of auto shredder residue
Currently, nearly all ASR is landfilled and a small portion is incinerated,
primarily owing to the lack of cost-effective technology to process and use ASR
(Argonne, 2003). An additional barrier to using it as fuel is that unprocessed ASR
has high ash, heavy metal, and chlorine content (Boughton, 2006).
Approximately 20 to 50 percent of dry ASR is combustible, including plastics,
fabric, and rubber; incombustibles include metals, glass, dirt, and ash. The first
step in processing ASR for fuel use would be removal of incombustibles (Tai,
2006; Boughton, 2006).
Auto Shredder Residue
ASR could potentially be used as a supplement to conventional fuel in cement
kilns or steel mill blast furnaces. Use of ASR in cement kilns may be more easily
accomplished than in boilers and other combustion units because kilns can
tolerate high ash content and heterogeneous materials. A recent evaluation of
ASR use in cement kilns conducted by the California Department of Toxic
Substances Control suggests that, despite the obstacles of separating combustibles
from incombustibles and reducing contaminant concentrations, processing ASR
for use in cement kilns would be cost-effective, due largely to the avoided
transportation costs and tipping fees associated with landfilling (Boughton, 2006).
This effect, however, would vary throughout the U.S. due to regional differences
in transportation distances and landfill tipping fees. In addition, the Environment
and Plastics Industry Council and the American Plastics Council have conducted
research investigating methods to process ASR into a more suitable fuel for steel
mill blast furnaces (Cirko, 1999).
(2) Non-combustion uses of auto shredder residue
As mentioned above, nearly all ASR is landfilled, and it appears that virtually no
ASR is currently beneficially used. 40 CFR 761.62, “Disposal of PCB bulk
product waste,” states, however, that ASR may be disposed in landfills as daily
cover or used under asphalt as part of road bed, but no data on such applications
have been identified. In addition, other potentially recoverable materials
contained in ASR and their potential uses include:
• Foam, which accounts for 5 percent of vehicles by weight but 30 percent
by volume, can be rebounded and used as carpet padding and seat cushions
in cars (DeGaspari, 1999).
• Plastics, which account for 30 percent of vehicle weight, can be recycled
into battery trays (Hook, 2008).
• Iron oxide residuals can be used as an ingredient in cement production
(3) Quantity of auto shredder residue landfilled
Sources generally state that most, if not all, ASR is landfilled (Hook, 2008; EPA,
2008; Boughton, 2006). This would suggest that approximately 5 million tons of
ASR are landfilled annually.
4. Management and Combustion Processes
(1) Types of units using auto shredder residue
Currently most ASR is landfilled, though development of methods to use ASR is
underway. Potential users of ASR include:
• Cement kilns
• Steel mill blast furnaces
• Car manufacturers
Auto Shredder Residue
(2) Sourcing of auto shredder residue
Approximately 12 to 15 million automobiles are disposed of annually in the U.S.
(USCAR, 2008). Once automobiles reach the end of their useful life, they are
sent to one of roughly 12,000 auto dismantlers, where the car is stripped of
reusable parts. The stripped cars are then sent to one of approximately 185 to 200
auto shredding operations, where hammermills crush them into smaller pieces.
Metal chunks are recovered and sold to metal scrap processing industries
(DeGaspari, 1999). Over 25 million tons of materials are recovered for reuse or
recycling. The remaining material comprises the ASR (EPA, 2008).
(3) Processing of ASR for combustion uses
Unprocessed ASR has poor fuel characteristics, due to its high ash content; the
presence of contaminants, including heavy metals, chlorine, and PCBs; and the
heterogeneity of ASR, which is made up of approximately 20 to 50 percent
incombustibles (Tai et al, 2006; Boughton, 2006). Prior to use as a fuel, ASR
would therefore require significant separation and processing to isolate
combustible materials with low ash content and low contaminant concentrations.
The California Department of Toxic Substances Control has developed methods
for separating and beneficiating the ASR stream to make it suitable fuel for
cement kilns. First, trommels are used to create ASR sub-streams of different
sizes, which also results in some rough separation by material (e.g., residual metal
fines are small, while plastic and rubber pieces are larger). Then further
separation is performed by hand and through density separation techniques, with
the goal of developing a mixture of ASR that maximizes energy content, while
minimizing content of ash, chlorine, and heavy metals. This process achieves a
mixture of ASR that represents 30 percent of the original mixture and has a
heating value of approximately 13,240 Btu per pound, which is higher than that of
most types of coal (Boughton, 2006).
The Environment and Plastics Industry Council and the American Plastics
Council coordinated with eight automobile shredders to develop a procedure for
processing ASR for use in steel mill blast furnaces. This process, which would
reduce the ash content of ASR and increase its energy content, would yield an
ASR material with a thermal value of approximately 10,000 Btu per pound
Researchers in Taiwan have taken further steps in the development of ASR for
fuel use by processing it into ASR-derived fuel (ASRDF) rods, for ease of
transportation and storage. The first step in this process is the manual removal of
glass, electrical wires, dirt and gravel, and metal components, yielding an ASR
mixture with a heat value of approximately 10,500 Btu/pound. Then the ASR is
placed into an extrusion apparatus, where it is exposed to high pressure and
temperature and formed into rods. The extrusion process reduces the heat value
Auto Shredder Residue
by approximately 1,800 Btu/pound, but the rods have a higher heat per unit of
mass than does the un-compacted material (Tai et al, 2006).
(4) Processing of ASR for non-combustion uses
As indicated above, virtually no ASR is used for non-combustion applications
because of the heterogeneity of ASR material. The Department of Energy’s
Argonne National Laboratory, however, has recently developed methods for
separation, recovery, and use of ASR. After undergoing separation and cleaning
processes, certain constituent materials of ASR can be recovered. Argonne has
found that up to 60 percent of ASR can be recovered as usable material (Hook,
The process developed by Argonne begins with bulk separation through use of a
two-part trommel, which separates ASR into three streams: a polymers-
concentrated stream (45 percent of ASR, by weight), foam (10 percent), and small
inorganic particles (45 percent). The first part of the trommel is equipped with a
fine mesh, through which the inorganic particles are separated. The second part
of the trommel has larger slots, through which plastics and rubber pieces fall,
leaving behind the foam. Each of these three streams is then further processed to
extract the useful materials. The polymers undergo density separation and froth-
flotation to be separated by type, in order to recover those plastics and rubbers
that are present in the largest volumes or that have the highest value. The foam,
which contains automotive fluids and some residual inorganic particles, is run
through a series of stages for cleaning, and is then dried and baled. The inorganic
particles, which include metal residuals, dirt, and glass, are exposed to magnets to
extract iron oxides, and the rest is discarded (Argonne, 2003; DeGaspari, 1999)
At present, Argonne’s system is not yet used in the United States, though it has
been licensed to Salyp N.V., a recycler in Belgium, which completed construction
of an ASR recycling plant in 2003 (DeGaspari, 1999; Hook, 2008).
(5) State regulatory status of auto shredder residue beneficial use
According to state responses to a 2006 survey by the Association of State and
Territorial Solid Waste Management Officials (ASTSWMO), Florida has
approved ASR as landfill initial cover, while Kentucky, Maryland, Massachusetts,
Michigan, New Hampshire, New York, Tennessee, Virginia, and Wisconsin have
approved it as an alternate daily landfill cover. ASTSWMO also reports that
Michigan and Texas have approved ASR for liquid solidification. Wisconsin has
pre-approved ASR for landfilling and Washington has pre-approved ASR in a few
cases as alternative daily cover (ASTSWMO, 2007).
5. Commodity Composition and Impacts
(1) Composition and energy content of auto shredder residue
30 percent polymers (by weight)
Auto Shredder Residue
10 percent residual metals
5 percent foam
The remainder is a mixture of glass, wood, paper, sand, dirt, rocks, and
automotive fluids (Hook, 2008; DeGaspari, 1999)
(b) Energy content:
Unprocessed ASR – roughly 5,000 Btu/pound (Boughton, 2006)
After removal of incombustibles – 9,000-10,500 Btu/pound (Tai et al,
2006; Cirko, 1999)
After removal of incombustibles and additional processing to isolate
combustibles with high energy content - 13,240 Btu/pound (Boughton,
(2) Impacts of auto shredder residue use
a. Cost impacts
The recycling and use of ASR may result in cost savings. The California
Department of Toxic Substances Control conducted an economic analysis of ASR
use in cement kilns, and found that the processing and use of all annually-
generated ASR for cement kilns would save the cement manufacturing industry
$50 million per year through reduced energy costs. It would also save auto
shredding operations $20 million per year in avoided landfilling costs. While the
costs of processing the ASR for use in cement kilns would also amount to $20
million per year, auto shredding operations could also generate $20 million per
year in revenue from the sale of copper, which is extracted during processing
(Boughton, 2006). Alternatively, if all ASR were to be used as a fuel in steel mill
blast furnaces, it could reduce fuel costs for operators by as much as $20 per ton
of coke replaced (Cirko, 1999). 1
Regarding the use of ASR for non-fuel applications, savings could be achieved
through avoided production of virgin foam. While clean recycled foam sells for
$0.25 to $0.30 per pound, virgin foam costs approximately $1 per pound
(Argonne, “Recovering Foam from Scrapped Autos”). In addition, the savings
referenced above with respect to copper recovered from ASR prior to its use as a
fuel would presumably apply to beneficial use for non-fuel applications as well.
Savings could also be realized through the re-use of other materials contained in
ASR, but no information on these savings has been identified.
b. Environmental impacts
Comprehensive data on the environmental impacts of using ASR as a substitute
for virgin materials have not been identified. Available data sources, however,
contain the following information regarding these impacts:
The figures presented in this paragraph could change over time, owing to variations in virgin fuel prices,
landfilling costs, and the value of copper. The California Department of Toxic Substances Control assumed the
following prices and values: a price of $50/ton of coal, landfilling tipping fee of $17/ton, trucking cost of $2/mile,
average distance to landfill of 20 miles, and $0.85/pound value of scrap copper wiring.
Auto Shredder Residue
• Argonne estimates that the recovery and reuse of polymers and residual
metals, for non-fuel applications, from all of the ASR produced annually in
the United States would save the equivalent of 24 million barrels of oil per
year and reduce CO2 emissions by 12 million tons (Hook, 2008). 2
• Benefits from the use of ASR as a fuel may also include reduced CO2
emissions from substitution for coal (Boughton, 2006). The California
Department of Toxic Substances Control estimates that if all ASR produced
in the United States were processed for use in cement kilns, it could
potentially provide 6 percent of the cement industry’s energy needs and
result in the conservation of approximately one million tons of coal
• Additionally, diverting ASR from landfills prevents potential leachate
contaminated with ASR constituents (Boughton, 2006).
It is important to note that the presence of contaminants in ASR raises concerns
about emissions from the combustion of this material. The California Department
of Toxic Substances Control found that, while its processing techniques for
developing ASR as a fuel for cement kilns minimizes contaminant concentrations,
chlorine and heavy metals still remain at levels that may limit the rate at which
ASR may be fed into a cement kiln (Boughton, 2006). Additionally, although
ASRDF rods have low heavy metals concentrations, the chlorine content of these
rods may represent a potential hazard (Tai et al, 2006). 3 Additional efforts to
eliminate PVC from ASR prior to its combustion for fuel purposes may mitigate
chlorine-related contamination issues, given that PVC is typically 50 percent
chlorine (Boughton, 2006).
It is unclear whether these figures represent estimates of direct or lifecycle energy and emissions impacts.
In addition, it is unclear whether this CO2 emissions value is net of the emissions associated with burning ASR.
In the Taiwanese study, no efforts were taken to remove combustibles with high chlorine contents, so
chlorine contamination is more of a concern than in the California study. Yet, in the Taiwanese study, metals were
removed more thoroughly by hand, so the rods present less of a threat of metal concentrations.
Auto Shredder Residue
Argonne. 2003. “Materials Recovery from Auto Shredder Residue.”
Argonne. “Recovering Foam from Scrapped Autos.” Argonne National Laboratory
Association of State and Territorial Solid Waste Management Officials (ASTSWMO). 2007,
2006 Beneficial Use Study Report, published by Association of State and Territorial Solid
Waste Management Officials.
Boughton, Robert. 2006. “Evaluation of shredder residue as cement manufacturing feedstock.”
California Department of Toxic Substances Control.
Cirko, Cathy. 1999. “Auto shredder residue potential fuel for steel mill blast furnaces.”
Canadian Chemical News, September 1, 1999.
DeGaspari, John. 1999. “From trash to cash: A new process reclaims former unrecoverables in
the residue of scrapped vehicles.” Mechanical Engineering Magazine Online
Hook, Brian R. 2008. “Auto shredder residue recycling researched.” AmericanRecycler.com
Nourreddine, Menad. 2007. “Recycling of auto shredder residue.” Journal of Hazardous
Materials 139(3): 481-490.
Tai, Hua-Shan, Sheng-Cheng Chang, and Wan-Shan Su. 2006. “Investigation of the Derived
Fuel Rod Formation from Auto Shredder Residue Using an Extrusion Apparatus.”
Environmental Progress 25(3): 235-252.
United States Council for Automotive Research LLC (USCAR). 2008. “Did you know that cars
are the most recycled product in America?” Press Release of USCAR
United States Environmental Protection Agency (EPA). 2008. “Automotive Parts,” at Common
Wastes & Materials <http://www.epa.gov/epawaste/conserve/materials/auto.htm>.